Ms Hatfield Dodds says the coalition's plans to reduce jobs in the public service is troubling Canberra voters.

"I met recently with the head of the Canberra Business Council and you know she was saying to me it's an issue for business across Canberra, every single business across Canberra is dependent on the public sector either directly or indirectly," she said.

But it is not certain that the Greens can prise votes away from Liberal Senator Gary Humphries.

"It's a tough ask but I think it's possible... the ducks have lined up in a way they haven't before," she said.

There is certainly momentum behind her. Ms Hatfield Dodds is a high-profile candidate who has deep roots in Canberra and who has built a national presence as a social justice campaigner.

But Senator Humphries says the Greens have a history of trumpeting polling results that turn out to be wide of the mark.

"Don't forget that they had a poll at the last election which purported to show that the Greens were easily going to win the seat," he said.

"The poll was spectaularly wrong when election day rolled in, the poll exaggerated the difference between the Liberal and Labor parties by almost 20 percentage points."

The Greens' vote has been building steadily in the ACT, and a Senate seat is now tantalisingly close to their grasp. The party won 21.5 per cent of the upper house vote in 2007 and is throwing considerable resources into the contest this time around.

"In 2007 the Greens candidate Kerrie Tucker missed out by around two thousand votes so it's a lot closer than people might believe."

But there's a catch.

The Greens aren't going to get more primary votes than Labor or the Liberals. That means they are going to have to strip those 2,000-plus votes off their weaker opponent - the Liberals - and rely on preferences to get them over the line.

If they don't force the Liberal vote well below the quota for a Senate seat, which is 33.3 per cent, then it's game over.

Gary Humphries is a moderate, popular local representative. He has always had a sensitive antenna for local issues, a strong contrarian streak and a hairy-chested turn of phrase when it comes to the public service and ACT self-determination.

Voters of all persuasions remember his decision to cross the floor and vote against his colleagues when they vetoed same sex civil union laws in the ACT in 2006.

He is also thoughtful and readily accessible. All of this has earned him widespread respect and allowed him to carve out a secure niche in Canberra's local political landscape. He'll be hard to dislodge.

And while the Liberal's senate primary vote isn't large in Canberra, it is resilient. It's never dropped below 30 per cent.

It's a fundamental human yearning to be a part of something bigger than one's self, and maybe that's what drove my mate Ash to die, far from home, in a bloody foreign war against Islamic State, writes C August Elliott.